The aim of this porposal is to assess the feasibility of using digital angiography to evaluate the severity of coronary artery disease. Quantitative methods to be studied will include those designed to measure anatomic coronary artery narrowing, myocardial perfusion abnormalities and segmental myocardial wall dysfunction induced by myocardial ischemia. Results will be compared to the computer-assisted method of measuring lesion dimensions from standard contrast angiograms previously developed by Brown, et al. One quantitative method to be evaluated will involve the use of videodensitometric as well as image border methods for measuring anatomic coronary artery narrowing from digital subtraction angiograms obtained following intracoronary injection of contrast material. Both methods will be used to measure the minimum lumen diameter (and area) of coronary artery lesions. We also will attempt to develop less invasive methods for obtaining coronary angiograms and quantitating the severity of coronary stenosis following injection of contrast material into the aortic root. Image processing algorithms to be evaluated in these low contrast images will include band pass filtering of electrocardiogram-gated images and a two-dimensional background interpolation method. The accuracy of these methods will be tested in phantom, dog and clinical models. A second general quantitative method for assessing the severity of coronary artery disease will entail evaluating myocardial perfusion using videodensitometry to generate contrast density versus time curves in myocardial regions supplied by individual coronary arteries. Data obtained from segments of myocardium supplied by stenotic coronary arteries will be compared to data from segments supplied by non-stenotic arteries. Studies will be performed in dogs and humans. The third general method for evaluating coronary artery disease involves the use of digital subtraction angiography to obtain left ventricular angiograms as a means of assessing global and segmental systolic and diastolic ventricular function at rest and immediately following atrial pacing in humans. The myocardial perfusion and segmental wall motion methods both will be related to the minimum lumen diameter of lesions in coronary arteries supplying each myocardial segment. If successful, these studies will provide improved methods for assessing the presence and severity of coronary lesions during routine clinical evaluation of patients with suspected coronary artery disease.